Its simple enough, this is where you can register for free to read this evolving book. I don't have a set methodical method for what will be visible on the internet to everyone and what will be available only to registered members, but it will probably be something like every other chapter.
Once the audio versions of the chapters are created, those will likely only be available to registered members (draft versions).
Update - This month, I'm also going to take a look at publishing an iPad and Kindle version of the chapters. More to follow . . .